Within this application, several publications are referenced by arabic numerals within parentheses. Full citations for these, and other, publications may be found at the end of the specification immediately preceding the claims. The disclosures of all these publications in their entireties are hereby incorporated by reference into the present application for the purposes of indicating the background of the present invention and illustrating the state of the art. Additionally, the disclosures of the following U.S. Patents and patent applications are hereby incorporated by reference for purposes of indicating the state of the art with respect to backlighting systems: U.S. Pat. No. 5,390,276, entitled "Backlighting Assembly Utilizing Microprisms and Especially Suitable for Use with a Liquid Crystal Display"; U.S. Pat. No. 5,359,691, entitled "Backlighting System with a Multi-Reflection Lighting Injection System and Using Microprisms"; U.S. Ser. No. 08/595,307, entitled "LCD with Light Source Destructuring and Shaping Device"; U.S. Ser. No. 08/601,133, entitled "Liquid Crystal Display System with Collimated Backlighting and Non-Lambertian Diffusing"; U.S. Ser. No. 08/618,539, entitled "Method of Making Liquid Crystal Display System"; and U.S. Ser. No. 08/782,962, entitled "Apparatus for LCD Backlighting." Finally, the disclosures of the following U.S. Patents are hereby incorporated by reference for purposes of indicating the state of the art with respect to diffuser systems: U.S. Pat. No. 5,534,386, entitled "Homogenizer Formed Using Coherent Light and a Holographic Diffuser" and U.S. Pat. No. 5,609,939, entitled "Viewing Screen Formed Using Coherent Light."
Generally speaking, multifaceted optical systems are systems in which there are a large number of small optical elements. Examples of multifaceted systems include composite mirrors and kaleidoscopes. Folded path systems are systems in which a light ray travels in multiple directions (or in a folded path), in contrast to single axis systems in which there is just one principal direction of the light beam. (The term "folded path" is used interchangeably with the term "multiaxial".) For example, a conventional periscope is multiaxial but is not multifaceted. Backlighting systems, such as those used with laptop computer screens, are both multifaceted and multiaxial.
Ray tracing is known for modeling lighting systems. A number of computer programs are available for performing such ray tracing, including Code V, OPTICAD, Radiance, and others.
Whenever performing ray tracing for lighting systems which are multiaxial or multifaceted or both, a large amount of rays is required to accurately trace the lighting system (at least 10,000 rays, and often 1,000,000 or more). The amount of computing time required by existing ray tracing programs to perform such complex ray tracing tasks is substantial. For example, in order to perform a ray tracing involving 100,000 rays, OPTICAD requires one to ten hours of computing time using a single computer.
The amount of computing time required to perform ray tracing is even greater for a substantial number of more complicated multiaxial and/or multifaceted lighting systems. Such systems include backlighting for laptop computer screens, dome lights in automobiles, and torus lighting structures used for ignition key lighting systems. All of these more complicated lighting systems require on the order of 1,000,000 rays in order to perform an accurate ray tracing. To perform such a ray tracing, about one day of computing time is required.
In nearly every industry, an emerging trend is the trend away from mass production and toward specialized product variations for individual customers. For example, in the context of backlighting systems for laptop computer-screens, each manufacturer of laptop computers is beginning to have slightly different backlighting specifications for each type of laptop computer manufactured. As a result, all types of laptop computers do not use exactly the same backlighting system. Rather, there are slight variations in terms of size and/or performance parameters of the backlighting systems. Thus, although mass production still exists, there is a move away from the "one size fits all" mentality which has characterized manufacturing and production in the past.
As a consequence of the trend towards greater product specialization, a subsidiary trend is the trend towards rapid prototyping. Prototyping is known in the context of product development for testing a product design before a product goes into mass production. Prototyping is done to ensure that the product is acceptable and will satisfactorily meet customer needs. Previously, a substantial amount of time could be devoted to the prototyping process. Once a product was developed, it was sold on a "one size fits all" basis to customers who did not ask to have products specially developed to optimally meet their special needs. With the trend toward product specialization, it is no longer acceptable to devote a substantial amount of time to the prototyping process. Product designs change rapidly and the "shelf life" of any given design tends to be shorter. From the customer's perspective, the benefits of purchasing a specially developed product as compared to an already existing product are lost if doing so results in a substantial delay due to prototyping times. Manufacturing customers have their own production schedules which must be met.
In the case of lighting systems, as is the case generally, it is necessary to prototype each product variation. This is because the product is sufficiently complex that slightly changing even just one parameter can drastically affect the overall performance of the product.
In view of the trend towards product specialization, it is apparent that the prototyping process should take as little time as possible. Consequently, for rapid prototyping, the use of ray tracing programs which take an entire day to ray trace a single lighting system prototype is unacceptable. It usually requires about one hundred separate iterations of the prototyping process to arrive at a lighting system prototype which in all respects satisfies customer needs. If it takes one day to ray trace one prototype, and if there are one hundred iterations of the prototyping process, then the resultant length of the prototyping process is at least one hundred days. This is in conflict with the basic concept of rapid prototyping, which is to provide a final design within days or weeks and not months.
Therefore, in order to make rapid prototyping possible in the context of multiaxial and/or multifaceted lighting systems, it is apparent that the amount of time required to perform one iteration of the prototyping process needs to be reduced dramatically, e.g., by a factor of one hundred. Indeed, since more than one hundred iterations are often required to produce an acceptable prototype, it is apparent that a reduction of greater than a factor of one hundred is even more desirable.
Moreover, it should also be the case that there is only one prototyping/design stage. In other words, once computer prototyping is complete, the prototype produced should satisfy customer needs in all respects. Thus, there should be only a single fabrication stage. It is undesirable to have to fabricate a physical prototype in order to learn of hidden defects, because the process of fabricating a physical prototype is time consuming and expensive as compared to computer prototyping.
Rapid prototyping thus far has not been applied to the development of lighting systems in general, and to ray tracing in particular. Existing ray tracing programs such as Code V implement very precise single ray tracing schemes. Other programs, such as Opticad and Radiance, apply conventional statistical methods (e.g., the Monte Carlo method) to implement a statistical multiray trace algorithm. All of these programs are slow and, moreover, none of these programs transfers the data which is produced into a convenient format. For example, although these programs generate ray coordinate, direction, and density information, these programs do not convert this information into photometric quantities so that the design engineer can easily assess the qualitative performance parameters of the final product. Also, there is no known method of transferring ray tracing information into three-dimensional visual imaging when the visual image surfaces are unknown. Also, there is no known method applying computer networks to ray tracing to reduce computation time.